Article feeding apparatus

ABSTRACT

An apparatus for feeding semiconductor chips has a structural body having grooves which serve respectively as parallel feed paths for semiconductor chips, the feed paths corresponding to respective quality levels of the semiconductor chips, the structural body being made of partially stabilized zirconia. A stopper mechanism for temporarily stopping semiconductor chips fed along the feed paths comprises piezoelectric bodies disposed in the feed paths in front of terminal walls of the feed paths. A counter mechanism for counting semiconductor chips fed along the feed paths have electrodes disposed in the feed paths near the terminal walls. The apparatus serves as a feed system for floating articles with ejected air and feeding the floated articles, and lends itself to being automatized.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an article feeding apparatus forfeeding articles (various electronic parts such as semiconductor chips)being fabricated to a next manufacturing process or feeding completedarticles to a next assembling process.

2. Description of the Related Art

Generally, production lines for articles (various electronic parts suchas semiconductor chips) often employ containers in the form of upwardlyopen boxes for feeding a number of articles to a next fabricationprocess or a storage chamber.

For feeding a number of electronic parts (hereinafter also referred toas “workpieces”) with a container along a production line, theworkpieces are randomly placed into the container, and the container isautomatically delivered to a next fabrication process or a storagechamber by a belt conveyor or a feed arm.

If articles to be fed are small-size articles such as electronic parts,then it is known to employ a feed path having a number of small holesand ejecting air through these holes to feed the articles.

According to the air-feeding process, a number of small-size articlescan smoothly be fed to a destination within a reduced period of timewhile reducing foreign matter which would otherwise tend to be attachedto the articles.

The air-feeding process is carried out by a feeding apparatus which isusually made of a metal such as aluminum or steel to meet robustnessrequirements of the feeding apparatus. However, it is not easy to formsmall air-ejection holes in the metal panel of the feed path forcontrolling a floated state of small articles to be fed. When thefeeding apparatus is used for a long period of time, the feed path,which is in the form of a groove, tends to be worn, and particlesabraded off the feed path are liable as foreign matter to the articlesbeing fed.

SUMMARY OF THE INVENTION

It is therefore an object of the present invention to provide an articlefeeding apparatus which has an automatized feed system for floating andfeeding articles of small dimensions in one direction with air, andwhich can handle articles in a clean state without producing foreignmatter such as small dust particles.

According to the present invention, there is provided an apparatus forfloating articles with ejected air and feeding the floated articles,comprising at least one feed path for feeding articles therealong in afeed direction, the feed path comprising a groove, a first layer havingside walls of the groove, a second layer serving as a bottom wall of thegroove and having a plurality of air ejection holes defined therein, athird layer having an air distribution passage for distributing air tothe air ejection holes, and a fourth layer serving as a bottom surfaceof the air distribution passage, at least the second layer being made ofa ceramic material. The ceramic material should preferably be, but notnecessarily limited to, partially stabilized zirconia for its strength.The apparatus serves as a feed system for floating articles with ejectedair and feeding the floated articles, and lends itself to beingautomatized.

Since the ceramic material can easily be shaped highly accurately whenformed, a plurality of small fluid ejection holes each having a diameterranging from several tens to several hundreds μm can be defined in thesecond layer for floating and feeding articles of small dimensions. Itis preferable to provide at least three fluid ejection holes per feedarea corresponding to one article.

If the first layer having side walls of the groove is made of a ceramicmaterial, then it can be shaped accurately to small dimensions. Forexample, if semiconductor chips each of a square shape having a size ofabout 0.2 mm×0.2 mm is to be fed, then grooves as feed paths can bedefined in the first layer at a small pitch of about 0.5 mm. The articlefeeding apparatus may be small in size. If an insulative ceramicmaterial is used, then electrodes may easily be formed on the layers byprinting or the like.

All the layers including the third and fourth layers may be formed of aceramic material. For example, if all the layers are formed and sinteredseparately and then bonded into a unitary assembly, then the unitaryassembly is free of problems such as of warpage or the like due tothermal expansion and shrinkage which would otherwise occur if thelayers are made of different materials. Alternatively, formed sheets ofthe layers may be laminated together and then sintered. This latterprocess is preferable because no bonding process is required and thelayers can be manufactured inexpensively and handled cleanly.

In the article feeding apparatus, furthermore, the first layer maypreferably be made of glass or synthetic resin. If electrodes of a metalmaterial are formed on the surface of the second layer which has beenformed and sintered, the first layer to be placed on the second layerand then sintered needs to be sintered at a temperature lower than themelting point of the second layer if the second layer is made of aceramic material. In view of this limitation, it is preferable to makethe first layer of glass or synthetic resin which has a low meltingpoint, and to print or coat a sheet of the first layer on the secondlayer on which electrodes have been printed, and then sinter the sheetof the first layer. Making the first layer of glass is preferablebecause it is resistant to wear. The application of a sheet of the firstlayer to the second layer is not limited to the printing or coatingprocess, but may be carried out by bonding a formed sheet of glass orsynthetic resin to the second layer with an adhesive. The glass orsynthetic resin is not limited to any particular type.

The article feeding apparatus also has a stopper mechanism a stoppermechanism positioned at a terminal end of the feed path, for temporarilystopping an article fed along the feed path, the stopper mechanismhaving at least a pair of piezoelectric bodies. The piezoelectric bodieshave upper ends held at a height slightly lower than the height to whichthe articles are floated. When a voltage is applied to the firstpiezoelectric body, it is deformed to lift its upper end to such aheight that the first piezoelectric body becomes a barrier in the feedpath. An article (first article) which has been fed hits the barrier andis temporarily stopped. Thereafter, the applied voltage is removed toallow the stopped article to be fed to a downstream unloading positionat the terminal end of the feed path where the article will be unloaded.The second piezoelectric body is positioned upstream of the firstpiezoelectric body, and temporarily stops a next article (secondarticle) positioned behind (upstream of) the first article. One or moresecond piezoelectric body may further be provided upstream.

In conventional apparatus for feeding articles with air, since air isejected to feed the articles in one direction with no control effectedon the articles being fed, articles tend to be held closely against eachother at the terminal end of the feed path and hence cannot easily beunloaded. Therefore, it has been customary to unload semiconductor chipsindividually manually from the conventional apparatus, and the feedsystem of the conventional apparatus cannot be fully automatized.

According to the present invention, as described above, a voltage isapplied to the first piezoelectric body to reliably stop a first articletemporarily, and then removed to allow only the stopped article to befed to the downstream unloading position. When only the first article isfed downstream to the unloading position, a voltage is applied to thesecond piezoelectric body positioned upstream of the first piezoelectricbody for thereby decelerate and stop the second article, which is thusprevented from being continuously fed into overlapping relation to thefirst article. Consequently, the first article can easily be unloaded atthe unloading position.

The article feeding apparatus further comprises a counter mechanismdisposed in the feed path, for counting articles fed along the feedpath, the counter mechanism having electrodes for detecting a change ina voltage which is produced by a change in an electrostatic capacitancebetween the electrodes when an article passes over the electrodes. Countinformation from the counter mechanism is used to automatize the articlefeeding apparatus.

Usually, the article feeding apparatus has as many grooves as the numberof quality levels of articles to be fed, for use as feed paths. If thesefeed paths are associated with respective article unloading units, thensuitable counter mechanisms may be combined with the respective articleunloading units. However, facility cost and installation spaceconsiderations have prevented the feed paths from being associated withrespective article unloading units, but have actually allowed the feedpaths to share one or few article unloading units. Accordingly, articlesbelonging to the respective quality levels cannot individually becounted. According to the present invention, however, a voltage iscontinuously applied between the electrodes of the counter mechanism,and the electrostatic capacity between the electrodes varies dependingon whether an article passes over the electrodes or not. Such avariation of the electrostatic capacity is detected as a voltage change.Since the electrodes can easily be provided in each of the feed paths,articles belonging to the respective quality levels can individually becounted with ease. If the counter mechanism is positioned at anintermediate position in each of the feed paths, then the countermechanism may be used as a sensor for detecting when a certain number ofarticles remain stagnant between the unloading position and theintermediate position.

While being fed along the feed path, the preceding first article isconstantly pushed by and held against the following second article, andhence these articles cannot reliably be distinguished by the countermechanism. Therefore, the counter mechanism is placed in the unloadingposition at the terminal end of the feed path where the preceding firstarticle is reliably separated from the following second article. Thecounter mechanism thus positioned is effective in counting articles fedalong the feed path, without fail.

The above and other objects, features and advantages of the presentinvention will become more apparent from the following description whentaken in conjunction with the accompanying drawings in which preferredembodiments of the present invention are shown by way of illustrativeexample.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of an article feeding apparatus accordingto the present invention;

FIG. 2 is a perspective view of a feed path of the article feedingapparatus shown in FIG. 1;

FIG. 3 is a sectional perspective view taken along line III—III of FIG.2;

FIG. 4 is a plan view of the article feeding apparatus shown in FIG. 1;

FIG. 5 is an enlarged fragmentary plan view of a region in the vicinityof an end wall of the feed path shown in FIG. 4;

FIG. 6 is a cross-sectional view taken along line IV—IV of FIG. 5;

FIG. 7 is a fragmentary perspective view of a piezoelectric bodyaccording to a first embodiment;

FIG. 8 is a fragmentary perspective view of a piezoelectric bodyaccording to a second embodiment; and

FIG. 9 is a fragmentary cross-sectional view taken along line IX—IX ofFIG. 4.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

As shown in FIG. 1, an article feeding apparatus 10 has a plurality ofparallel grooves serving as feed paths 12 for feeding a number ofsemiconductor chips. The article feeding apparatus 10 has a structuralbody made of partially stabilized zirconia (PSZ), which includes aregion where the above grooves are defined.

The article feeding apparatus 10 serves to sort out semiconductor chipsaccording to their quality level. Specifically, after semiconductorchips on wafers 14 are inspected for quality, the wafers 14 are carriedto the article feeding apparatus 10, and the semiconductor chips areattracted one at a time under vacuum by a robot 16 a. Each of thesemiconductor chips is delivered by the robot 16 a to one of the feedpaths 12 depending on the quality level of the semiconductor chip.Therefore, each of the feed paths 12 is loaded with and feeds successivesemiconductor chips of a certain quality level. The semiconductor chipsthat have arrived at the terminal ends of the feed paths 12 areattracted under vacuum by a robot 16 b, and carried to and placed incases 18 a- 18 n assigned to the respective quality levels. Thereafter,the cases 18 a- 18 n are delivered to a next process.

The article feeding apparatus 10 basically comprises a mechanism forfloating charged semiconductor chips, a mechanism (propelling mechanism)for feeding floated semiconductor chips in a feed direction along thefeed paths 12, and a mechanism for reliably removing semiconductor chipsone at a time from the terminal end of each of the feed paths 12. One ofthe feed paths 12, which are identical to each other, is illustrated inFIG. 2.

In FIG. 2, the feed path 12 is associated with a mechanism for floatingcharged semiconductor chips 26, which mechanism is in the form of aplurality of air ejection holes 20 defined vertically in a feed panel ofthe feed path 12, for ejecting air upwardly therethrough. The feed path12 is associated with a mechanism (propelling mechanism) for feedingfloated semiconductor chips 26 in a feed direction, which mechanism isin the form of an air blowing pipe 22 connected to an air supply systemincluding an air pump and a solenoid-operated valve (not shown). The airblowing pipe 22 has a nozzle 24 mounted on its lower tip end forejecting air under a pressure of about 0.5 kgf/cm² toward asemiconductor chip 26 on the feed panel. The feed path 12 is alsoassociated with a mechanism for reliably removing semiconductor chips 26one at a time, which mechanism is in the form of a plurality of airejection holes 20 defined in the terminal end of the feed path 12,remote from the air blowing pipe 22, for ejecting air therethrough tofloat one at a time of the semiconductor chips 26, so that the floatedsemiconductor chip 26 can be attracted under vacuum and smoothly fed bythe robot 16 b (see FIG. 1). As can be seen from FIG. 2, the airejection holes 20 defined in the terminal end of the feed path 12 areprovided at a greater density than the air ejection holes 20 defined inthe remainder of the feed path 12.

An upstanding terminal wall 28 disposed at the terminal end of the feedpath 12 has a plurality of parallel vertical slits 30 defined therein.The slits 30 prevent foreign matter from being accumulated against theupstanding terminal wall 28 and hence from being applied tosemiconductor chips 26 when they arrive at the terminal end of the feedpath 12.

Since the article feeding apparatus 10 is made of a ceramic material, itis prevented from being unduly worn and producing foreign matter as dustparticles.

The mechanism (propelling mechanism) for feeding floated semiconductorchips 26 in the feed direction may alternatively comprise means fortilting downwardly the feed path 12 through a predetermined angle withrespect to the feed direction. When the feed path 12 is tilteddownwardly, floated semiconductor chips 26 are fed by gravity down thefeed path 12.

The air ejection holes 20 may be defined obliquely in the feed panel ofthe feed path 12 for ejecting air upwardly and toward the feed directiontherethrough. The air thus ejected from the air ejection holes 20 imparta floating force and a propelling force to semiconductor chips 26 in thefeed path 12.

The mechanism for reliably removing semiconductor chips 26 one at a timemay alternatively comprise means for designing a planar shape of thefeed path 12 in order to maximize the lift of the semiconductor chips 26near the terminal wall 28. Specifically, the air ejection holes 20defined in the terminal end of the feed path 12 may be provided at thesame density as the air ejection holes 20 defined in the remainder ofthe feed path 12, and the planar shape of the feed path 12 may bedesigned to make an amount of air leaking through the gap between asemiconductor chip 26 and the feed path 12 at the terminal end of thefeed path 12 smaller than the amount of air leaking through the gapbetween a semiconductor chip 26 and the feed path 12 in the remainder ofthe feed path 12.

To prevent foreign matter from being attached to semiconductor chips 26,the terminal wall 28 may have protrusions thereon projecting towardsemiconductor chips 26, i.e., upstream in the feed direction, so thatthe protrusions will be held in point-to-point contact with asemiconductor chip 26 as it arrive at the terminal end of the feed path12.

As shown in FIG. 3, the structural body of the article feeding apparatus10 includes first, second, third, and fourth layers 31 a, 31 b, 31 c, 31d successively arranged downwardly. The first through fourth layers 31 a14 31 d are all made of partially stabilized zirconia. The first throughfourth layers 31 a- 31 d may be manufactured either by forming sheets ofthe ceramic material, integrally joining the sheets, and sintering thejoined sheets, or by sintering separate sheets of the ceramic materialand bonding the sintered sheets together.

The first layer 31 a has a plurality of parallel spaced narrow groovesdefined therein as the feed paths 12 by side walls thereof. For example,if each of the semiconductor chips 26 is of a square shape having a sizeof about 0.2 mm×0.2 mm, then the narrow grooves as the feed paths 12 forfeeding such semiconductor chips 26 are defined at a pitch orcenter-to-center distance of about 0.5 to 0.7 mm, the narrow grooveseach having a width (W) ranging from about 0.2 to 0.3 mm. The narrowgrooves as the feed paths 12 can be defined with high dimensionalaccuracy. Since the feed paths 12 are very small in size, therefore, thearticle feeding apparatus 10 may be small in size.

The second layer 31 b, which serves as a bottom wall of each of the feedpaths 12, has a number of air ejection holes 20 defined therein, andalso has a plurality of electrodes 32 a- 32 c supported thereon whichare electrically connected to a piezoelectric body (described later on).Each of the air ejection holes 20 is of a very small diameter, e.g., inthe range from 10 to 120 μm. The electrodes 32 a- 32 c may easily beprinted on the second layer 31 b. The air ejection holes 20 arepreferably provided at such a density that three air ejection holes 20are assigned to each semiconductor chip 26.

The third layer 31 c has a plurality of air distribution passages 34defined therein for distributing air to the air ejection holes 20 in thesecond layer 31 b. The air distribution passages 34 extend parallel toeach other along the feed paths 12 and are connected to respective airsupply holes 36 defined in the fourth layer 31 d. The third layer 31 cmay instead have a single air distribution chamber associated with allthe feed paths 12.

The fourth layer 31 d serves to provide bottom surfaces of the airdistribution passages 34. The air supply holes 36 in the fourth layer 31d have upper ends opening into the air distribution passages 34. The airsupply holes 36 may be defined in side walls of the third layer 31 c,and the fourth layer 31 d may be in the form of a sheet with no holesdefined therein.

The second layer 31 b needs to be made of a ceramic material such aspartially stabilized zirconia. However, the third layer 31 c and thefourth layer 31 d are not limited to the same ceramic material as thesecond layer 31 b though the third layer 31 c and the fourth layer 31 dwhich are made of the same ceramic material as the second layer 31 b arefree of problems such as of warpage or the like due to thermal expansionand shrinkage.

If the electrodes 32 a- 32 c are printed on the second layer 31 b andthe electrodes 32 a- 32 c are made of a cermet material which comprisesa metal such as platinum and a ceramic material such as partiallystabilized zirconia diffused in the metal, then the first layer 31 a maybe made of a ceramic material. If the electrodes 32 a- 32 c are made ofa metal such as gold or platinum, then the first layer 31 a may beproduced by printing a glass material and then sintering the printedglass material or by bonding a synthetic resin. This is because if thefirst layer 31 a were made of a ceramic material, it would melt themetal of the electrodes 32 a- 32 c when the first layer 31 a would besintered.

A stopper mechanism used in the article feeding apparatus 10 will bedescribed below.

As shown in FIG. 4, the article feeding apparatus 10 has ten grooves asfeed paths 12 which correspond respectively to the quality levels ofsemiconductor chips 26. Semiconductor chips 26 are charged into thearticle feeding apparatus 10 from a left-hand charging area in FIG. 4,and floated and fed along the feed paths 12 toward their terminal endsat a right-hand area in FIG. 4. Each of the feed paths 12 has a lengthof about 300 mm, and has first and second piezoelectric bodies 38 a, 38b at the terminal end of the feed path 12. The first and secondpiezoelectric bodies 38 a, 38 b serve as the stopper mechanism.

Each of the first and second piezoelectric bodies 38 a, 38 b preferablycomprises a film of piezoelectric ceramic material, but may comprise afilm of electrostrictive or ferroelectric ceramic material. The ceramicmaterial used may be a material which needs to be either polarized ornot. The first and second piezoelectric bodies 38 a, 38 b are fabricatedby printing the above ceramic material on a formed body of the secondlayer 31 b and then sintering the printed ceramic material together withthe formed body of the second layer 31 b. The ceramic material may belead zirconate, lead titanate, lead magnesium niobate, nickel leadniobate, lead zinc niobate, or the like, which may be used singly or incombination. Preferably, the first and second piezoelectric bodies 38 a,38 b are preferably made mainly of lead zirconate, lead titanate, andlead magnesium niobate because they have a high electromechanicalcoupling coefficient and a high piezoelectric constant, are lessreactive with the material of the article feeding apparatus 10 at thefirst and second piezoelectric bodies 38 a, 38 b are sintered, and canstably produce a desired composition.

As shown in FIG. 5, the first piezoelectric body 38 a is spaced upstreamof the terminal wall 28 by a distance which is slightly greater than thesize of a semiconductor chip 26, and the second piezoelectric body 38 bis spaced upstream of the first piezoelectric body 38 a is spacedupstream of the terminal wall 28 by a distance which is slightly greaterthan the size of a semiconductor chip 26. The second layer 31 b supportsthereon individual electrodes 32 a, 32 b and a common electrode 32 cwhich allow the first and second piezoelectric bodies 38 a, 38 b to forman electric circuit. The electrodes 32 a- 32 c are connected to a DCpower supply. The common electrode 32 c connected to the first andsecond piezoelectric bodies 38 a, 38 b has an upper end held in aposition which is about 3-5 μm lower than the height to which thesemiconductor chip 26 is floated. Electrodes 40 a, 40 b of a countermechanism are disposed in the vicinity of the terminal wall 28. Theelectrodes 40 a, 40 b will be described later on.

The electrodes 32 a- 32 c are made of an electrically conductive metalwhich is solid at normal temperature, such as gold, platinum, iridium,tungsten, tantalum, tin, silver, rhodium, or the like, which may be usedsingly or in combination. Alternatively, the electrodes 32 a- 32 c maybe made of a cermet material which comprises the same ceramic materialas the first and second piezoelectric bodies 38 a, 38 b or the thirdlayer 31 b that is diffused in the above material. The electrodes 32 a-32 c may be sintered of a material of a high melting point together withthe first and second piezoelectric bodies 38 a, 38 b, taking intoaccount the melting point of the material of the first and secondpiezoelectric bodies 38 a, 38 b, or may be produced separately after thefirst and second piezoelectric bodies 38 a, 38 b have been sintered of amaterial of a low melting point.

As shown in FIG. 6, the second piezoelectric body 38 b is sandwiched andbonded between the common electrode 32 c and the individual electrode 32b. In FIG. 6, the semiconductor chip 26 is fed to a position above thesecond piezoelectric body 38 b. The second layer 31 b comprises a thinfilm having a thickness of about 20 μm, and is sufficiently flexiblewith opposite ends clamped between the first layer 31 a and the thirdlayer 31 c.

As shown in FIG. 7, the first and second piezoelectric bodies 38 a, 38 bmay be disposed on the second layer 31 b, and the individual electrodes32 a, 32 b, which are comb-shaped, and the common electrode 32 c, whichis also comb-shaped, may be disposed in spaced interdigitating relationto each other on the first and second piezoelectric bodies 38 a, 38 b.

Alternatively, as shown in FIG. 8, the individual electrodes 32 a, 32 b,which are comb-shaped, and the common electrode 32 c, which is alsocomb-shaped, may be disposed in spaced interdigitating relation to eachother on the second layer 31 b, with the first and second piezoelectricbodies 38 a, 38 b disposed in the gap between the individual electrodes32 a, 32 b and the common electrode 32 c.

Operation of the stopper mechanism will be described below.

As shown in FIG. 9, when a voltage is applied to the first piezoelectricbody 38 a, it is mechanically deformed into a barrier having anincreased height in the feed path. When a floated semiconductor chip 26a collides with the barrier, the semiconductor chip 26 a which hastraveled to a position near the terminal end of the feed path istemporarily stopped. Then, the applied voltage is removed, allowing thefirst piezoelectric body 38 a to return to an original height thereofslightly lower than the height of the floated semiconductor chip 26 a.The stopped semiconductor chip 26 a. is now permitted to travel furtherdownstream to an unloading position at the terminal end of the feedpath. After the semiconductor chip 26 a. has been fed to the unloadingposition, a voltage is applied again to the first piezoelectric body 38a to stop a next semiconductor chip 26 b. The above cycle of operationwill subsequently be repeated.

When the first piezoelectric body 38 a returns to the original height,permitting the semiconductor chip 26 a to travel further downstream tothe unloading position, a voltage is applied to the second piezoelectricbody 38 b to impose frictional forces on the surface of the nextsemiconductor chip 26 b which is in contact with the secondpiezoelectric body 38 b thereby to decelerate and stop the semiconductorchip 26 b for preventing the semiconductor chip 26 b from being directlyfed to the unloading position and hence overlapping the semiconductorchip 26 a. Therefore, whereas a voltage is repeatedly applied andremoved from the first piezoelectric body 38 a in certain periodiccycles, a voltage is applied to the second piezoelectric body 38 bduring periods of time in which no voltage is applied to the firstpiezoelectric body 38 a and marginal periods before and after thoseperiods of time. Since the second layer 31 b on which the first andsecond piezoelectric bodies 38 a, 38 b are mounted is sufficientlyflexible, when voltages are applied to the first and secondpiezoelectric bodies 38 a, 38 b, the first and second piezoelectricbodies 38 a, 38 b are allowed to be deformed effectively without beingunduly constrained by the second layer 31 b.

For reliably allowing the first and second piezoelectric bodies 38 a, 38b to operate reliably as described above, the original thickness(height) of the first and second piezoelectric bodies 38 a, 38 b shouldpreferably be in the range from about 10 to 30 μm. The surface of thesecond piezoelectric body 38 b should preferably be coated with highlywear-resistant glass or resin film for increasing frictional forcesexerted thereby to the semiconductor chip 26 b.

The counter mechanism in the article feeding apparatus 10 will bedescribed below.

The counter mechanism is positioned in alignment with the firstpiezoelectric body 38 a or the second piezoelectric body 38 b in each ofthe feed paths 12. As shown in FIGS. 4 and 5, the electrodes 40 a, 40 bof the counter mechanism are disposed at the terminal end of each of thefeed paths 12 near the terminal wall 28 and transversely spaced fromeach other. The electrodes 40 a, 40 b are electrically connected torespective conductors 42.

Alternatively, as shown in FIG. 6, the common electrode 32 c may be usedas one of the electrodes of the counter mechanism, and an electrode 44may be mounted on the first layer 31 a over the common electrode 32 cfor use as the other electrode of the counter mechanism. With thisarrangement, some of the existing electrodes and circuit may be used aspart of the counter mechanism. Further alternatively, as shown in FIG.4, the electrodes of the counter mechanism may be located at anintermediate position in each of the feed paths 12, e.g., at the ninthsemiconductor chip 26, as counted upstream (away from the terminal wall28) from the terminal end of each of the feed paths 12, of a series ofnine semiconductor chips 26 staying in the feed path 12.

The electrodes 40 a, 40 b of the counter mechanism may be made of thesame material and may be manufactured in the same manner as theelectrodes 32 a- 32 c connected to the first and second piezoelectricbodies 38 a, 38 b, or may not be limited to the same material as theelectrodes 32 a- 32 c, but may be made of any of various ordinaryelectrically conductive materials.

The electrodes 40 a, 40 b of the counter mechanism operate as follows:

A voltage is continuously applied between the electrodes 40 a, 40 b.When no semiconductor chip 26 is present on the electrodes 40 a, 40 b, acapacitor with air serving as a dielectric medium is connected betweenthe electrodes 40 a, 40 b, and a voltage V₁ is detected between theconductors 42. When a semiconductor chip 26 is fed to a position nearthe terminal wall 28, i.e., over the electrodes 40 a, 40 b, as shown inFIG. 5, a capacitor with the semiconductor chip 26 serving as adielectric medium is connected between the electrodes 40 a, 40 b, and avoltage V₂ which is lower than the voltage V₁ is detected between theconductors 42. The voltage between the conductors 42 is continuouslydetected by a circuit (not shown) of the counter mechanism to count thenumber of times that the detected voltage varies, and the counter numbercan be recognized as the number of semiconductor chips 26 that have beenfed to the position near the terminal wall 28.

Since one at a time of semiconductor chips 26 is reliably fed to theposition near the terminal wall 28 by the stopper mechanism,semiconductor chips 26 are prevented from unduly overlapping each otheror being joined to each other at position near the terminal wall 28.Consequently, the number of fed semiconductor chips 26 can reliably becounted by the counter mechanism. Using the count information from thecounter mechanism, it is possible to control the rate at whichsemiconductor chips 26 are fed down the feed paths 12 for automatizingthe article feeding apparatus 10.

If the electrodes of the counter mechanism are be located at anintermediate position in each of the feed paths 12, as described above,then the counter mechanism may be used as a sensor for detecting when acertain number of semiconductor chips 26 remain stagnant between theunloading position at the terminal end of the feed path 12 and theintermediate position.

Although certain preferred embodiments of the present invention havebeen shown and described in detail, it should be understood that variouschanges and modifications may be made therein without departing from thescope of the appended claims.

What is claimed is:
 1. An apparatus which gas feeds electronic parts,comprising: a structural body having grooves which serve respectively asparallel feed paths for electronic parts, said feed paths correspondingto respective quality levels of the electronic parts, said structuralbody being made of partially stabilized zirconia; a stopper mechanismfor temporarily stopping electronic parts fed along said feed paths,said stopper mechanism comprising piezoelectric bodies disposed in saidfeed paths in front of terminal walls of the feed paths; and a countermechanism for counting electronic parts fed along said feed paths, saidcounter mechanism having electrodes disposed in said feed paths nearsaid terminal walls.